1. Chemical leaveners
There are two "oldfashioned" chemical leaveners, both still used today in traditional German and Scandinavian gingerbread recipes:
Potassium carbonate (potash or pearl ash) and
Ammonium bicarbonate (salt of heartshorn)
They do have their own quirks and pitfalls, but if nothing else is available...
If you can get baking soda, mix ...